Devices that release vapors into the air are well-known in the art. Generally, the purpose of such devices is to deodorize, disinfect, or add positive fragrance to the ambient air, or to distribute insect repellants or insecticides into the air to kill or repel unwanted pests.
Various types of devices have been employed to dispense vapors into the air. For example, passive dispensing devices are known, wherein a volatile material in a gel, liquid, or solid form is provided within a container. The volatile material is diffused into the surrounding atmosphere and the diffusion may be assisted by the natural airflow within the surroundings. An adjustable vent may be included in such passive dispensing devices to increase and decrease the amount of volatile material emitted from the passive dispensing devices. Aerosol containers have also been employed to eject droplets of volatile material from a pressurized container into a surrounding atmosphere upon activation of a trigger.
Other devices have utilized mechanical or electrical devices to disperse volatile materials into the atmosphere. For example, some devices include a cord and plug extending from the device, a plug extending directly from the device, and/or batteries, to power elements of the device. Such powered devices may include one or more heaters, fans, piezoelectric actuators, or other means, or combination thereof by which the volatile material is dispensed from the device.
One type of powered volatile material emitting dispenser includes a housing and one or more heaters and/or fans disposed within the housing for dispensing a liquid volatile material. The liquid volatile material is disposed within a refill having a container for holding the volatile material and a wick in contact with the liquid volatile material and extending out of the container. The wick is disposed adjacent the heater and/or fan when the refill is inserted into the dispenser. Such powered dispensers may be battery-powered or may include an electrical plug extending therefrom that may be inserted into a conventional electrical socket for powering same.
Volatile materials in the form of fragrances are oftentimes used with dispensers employing heaters. Fragrances generally consist of a number of components, combined in particular proportions to give an intended overall smell or character. Achieving this character during emission of a particular fragrance requires releasing the components at rates and in proportions that match their proportions in the original fragrance. This is much easier said than done. In practice, components of the fragrance have different volatilities where volatility is quantified by a partial pressure of a saturated vapor for each component. The greater the partial pressure, the greater the rate at which molecules are released from a surface of the liquid by evaporation. Dispensers employing evaporation therefore tend to emit the more volatile components in a greater proportion than less volatile components, so that the character of the emitted fragrance at any given point in time is not what was intended (in the original proportions). This evaporation of the more volatile components at a greater rate also changes the overall composition of the fragrance over time, thereby continually changing the composition of the fragrance remaining in the refill (as opposed to the original fragrance composition).
A process called fractionation occurs within the wick wherein, over time, fractionation reduces the concentration of high volatility fragrance components and increases the concentration of low volatility fragrance components at an emanating surface (presumably a tip of a wick and/or outer surface of the wick that is exposed to ambient air) and can lead to the vapor composition matching the original fragrance composition. In many dispensers, this process is too slow to be effective. In other words, fractionation takes many days, but in the first few days of use, an excessive amount of the high volatility components is emitted, thereby resulting in a change in the fragrance composition in the refill before fractionation sets in. Fractionation fails to equilibrate with the changing fragrance composition in the refill, thus resulting in the fragrance and vapor compositions steadily varying over time.